RE: [alfa] GTV-6 voltage drop

["Jeff Greenfield" <alfaguy@xxxxxxxxxxxx>]

Joe -

Could be a couple of things ...

Could be the alternator, regulator, diodes, or a wiring problem.

I had a similar problem with a Milano not all that long ago. Alternator
output was adequate without any loads on, but loaded up it was lower than it
should be. Put a rebuilt alternator in it, which helped but it still wasn't
right. Tried another alternator (hey, I keep one on the shelf), no
difference.

To make a long story short, there was too much resistance in the red wire
running from the back of the alternator to the junction block on the inner
fender. Replaced this length of wire with some decent quality 10 gauge and
the problem went away.

A simple check for alternator diodes, is to connect your multimeter across
the battery (or to any other convenient place), set the meter to measure A/C
on a low range (0-1 volt). You should read .5v or less, anything more
indicates bad diodes.

Here is a useful link for diagnosing automotive electrical systems with a
DMM

<http://www.fluke.com/application_notes/automotive/beatbook.asp?AGID=1&SID=1
03>

Click on charging systems ...

There is also a way to test the alternator on the car by getting it to go to
full output by bypassing the voltage regulator, but unless you know what you
are doing and are very careful with this procedure, you can do some serious
damage.

Jeff

-----Original Message-----
From: owner-alfa@domain.elided [mailto:owner-alfa@domain.elided] On Behalf Of Joe
Elliott
Sent: Monday, March 15, 2004 4:19 PM
To: Alfa Romeo Digest
Subject: [alfa] GTV-6 voltage drop

One of these days I'll post some pictures and tell you all about my
wonderful spring break trip to Italy last week, but for now I have an
actual car problem to discuss.

Long story short:  When my engine is running at 2000RPM with no
accessories on, I see 14.5V at the battery; When cooling fans,
aircon, and headlights are on, I see 12.5V.

Even at higher revs, there's a significant votlage drop when I turn
on the headlights for example.  My first thought was that there must
be a dirty connection somewhere--more current, bigger V drop across
that connection.  But my highbeams are switched by relays that are
right next to the junction block where the 8-gauge wire comes from
the alternator.  They are powered from that junction, and grounded
directly to the engine grounding strap.  So there's not much wire
involved with my highbeams, and I can pretty much see all of it, yet
turning the highbeams on produced similar results--what's going on
here?  Is my alternator shot?

Thanks,
Joe Elliott
'82 GTV-6
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